Fishing method and apparatus



Dec. 24, 1968 T. D. HOWELL FISHING METHOD AND APPARATUS Filed July 29, 1966 760.070.; 2 flan/e INVENTOR BY W a "m y a a .4 o I lll l i 4 v I I I1! filrflflvvrvvall r !fl v r w l l v l r I w J 2 w a a m a a a F x F JTTORNEY United States Patent 3,417,822 FISHING METHOD AND APPARATUS Thomas D. Howell, Bossier City, La., assignor to Tri- State Oil Tool Industries, Inc., Bossier City, La. Filed July 29, 1966, Ser. No. 568,862 11 Claims. (Cl. 16643) ABSTRACT OF THE DISCLOSURE A method and an apparatus for retrieving objects stuck in a. well bore which includes the establishing fluid circulation from the interior to the exterior of the retrieving string even though the lower end of the retrieving string is blocked.

Background of the invention As is well known, it often occurs that drill collars, drill strings or other objects become stuck in a well bore during drilling or other operations, and such an object is commonly called a fish. This sticking is usually caused by the collapse of the Well bore around the outside of the fish, and in many instances the bore through the stuck collar or string is also plugged. The general practice in attempting to free the stuck object, or fish, is to lower a fishing string having a retrieving assembly provided with means at its lower end for connection with the stuck objects, or fish. The retrieving assembly normally includes jars, a sub connecting the jars to a safety joint and below the safety joint is provided a connector sub or overshot for making connection with the upper end of the fish. By lifting the fishing string, an upward pull may be applied to the stuck fish, and since jare are included in the assembly, an upward jarring impact may "also be imparted to the stuck fish. In some instances, the upward pull and jarring are suflicient to remove or dislodge the fish.

In certain cases, particularly Where the bore of the stuck collar, string or other object is plugged with the formation material, a straight upward pull and jarring action is insufficient to effect the release. In such instance, it is then desirable to lower, usually by means of a wire line, a tool which includes a wash pipe whereby circulation may be directed downwardly through the fishing string to wash out the bore of the stuck fish. However, in order to use such a wash pipe and to complete circulation to the surface from the bore of the stuck object, it is necessary that circulation be established downwardly through the wash pipe and then upwardly in the annulus between the fishing string and the bore. With the usual type of retrieving assembly, there is no means for establishing the circulation between the bore of the fishing string and the annulus to permit this circulation, and it has, therefore, been necessary to disconnect the fishing string from the fish, remove it from the well and then insert a special sub having radial circulation ports in the retrieving assembly. Thereafter, the fishing string with the special sub in its retrieving assembly is again lowered into the well bore, and the fishing string and its retrieving assembly are reconnected with the fish. With the retrieving assembly reconnected to the fish, the Wash pipe may be lowered into position and circulation may be establised downwardly through the fishing string and wash pipe into the bore of the fish, then upwardly around the wash pipe and through the radial ports in the special sub and upwardly through the annulus between the fishing string and the well bore wall. By being able to, wash out the plugged bore, the chances of retrieving the fish by a subsequent upward pull jarring impact is enhanced and, in many instances, the recovery of the fish is effected. This operation requires an extra round trip of the fishing string and 3,417,822 Patented Dec. 24, 1968 has the additional disadvantage of difiiculty in reconnecting with the fish.

Summary The present invention relates generally to a new and improved method and apparatus for retrieving stuck objects in a well bore and more particularly to establishing a washing circulation during retrieving operations in a well bore.

It is, therefore, one object of this invention to provide an improved method for retrieving a stuck object from the well bore in which the fishing string may be lowered and attached to the stuck fish in the usual manner, after which an upward pull and impact jarring may be accomplished; if this is insufiicient to remove the fish, the method then contemplates establishing circulation between the bore at the fishing string and the annulus surrounding said string, whereby a washing operation may be carried out without having to disconnect the fishing string and its retrieving assembly from the fish; said method thereby eliminating the requirement for an extra round trip of the string and at the same time obviating the problems involved in having to reconnect said fishing string with the fish. Another object is to provide an improved method for retrieving a stock fish in the well bore which permits the normal upward pull and impact jarring to be performed, followed by a washing operation which will wash the bore of the plugged fish; the washing operation being accomplished by selectively establishing circulation, if such be necessary, between the bore of the fishing string and the annulus around said string within the bore.

Another object is to provide an improved method of the character described wherein the selective establishment of circulation between the bore of the fishing string and the annulus is controlled by the application or building up of a predetermined fluid pressure within the fishing string.

A further object of the invention is to provide an improved sub adapted to be connected as a part of the retrieving assembly in a fishing string, which sub has a normally closed opening so that the fishing string may be operated in a normal manner; the sub opening being selectively opened if and when it is desired to establish communication between the bore of the fishing string and the annulus surrounding said string.

Still another object of the invention is to provide an improved sub adapted to be connected into a retrieving assembly of a fishing string having a radial port which is normally closed and which, when opened, establishes communication between the bore of the string and the annulus; opening of the port being controlled by a predetermined pressure buildup within the fishing string, whereby circulation to wash out the plugged bore of the fish may be established, drilling mud may be pumped downwardly through the well bore and into the bore of the fishing string to control a blowout condition, or upon freeing the fish, the fluid within the fishing string may be released as the same is removed from the well bore, whereby the necessity of pulling a wet string is eliminated.

These and other objects and advantages will be apparent and explained in the following specification describing the present invention with reference to the drawings wherein:

FIGURE 1 is a longitudinal sectional view of a fishing string with its retrieving assembly connected to a fish and a wash pipe in position ready for establishing circulation to wash out the bore of the fish in accordance with the method of the present invention; and

FIGURE 2 is a partial longitudinal sectional view of the washout sub used in the retrieving assembly of the fishing string and showing details of a rupturable diaphragm used to normally close the communication between the interior and exterior of the sub.

As shown in FIGURE 1, the fish F is stuck in the well bore B. To remove the fish F, the prior practice has been to lower a fishing string S which includes a retrieving assembly R. The retrieving assembly R would normally include the connector sub or other suitable means for connecting with the fish F, the safety joint '12, the sub 14 connecting the safety joint 12 to the jars J and sections 16 of the fishing string on which the retrieving assembly R is lowered into the well bore B. When connection is achieved between the fish F and the connector sub 10, efforts are made to free the fish F by a lifting of the fishing string S and also by actuating the jars I. If such efforts free the fish F, it is withdrawn from the well bore.

It has been the practice when such efforts have not succeeded in freeing the fish F and where there is a possibility that the bore of the fish is clogged with formation material to attempt to wash the material from the bore of the fish with a wash pipe 18. The retrieving assembly R is provided with a central bore and defines the internal seat 20 on which the packing 22 of the wash pipe 18 seats. When seated in the retrieving assembly R, the tubular body 24 extends downwardly so that its nozzle 26 projects beyond the end of the retrieving assembly R into the bore of the fish F. To establish circulation in the past, it has been necessary to disconnect from the fish F, pull the fishing string S, replace the sub 14 with a different sub 14 having radial ports, lower the fishing string S into the well bore B and reconnect to the fish F. Thereafter, the wash pipe 18 is run by any suitable means, such as a wire line. With the wash pipe 18 in place, the fluid is pumped down through the bore of the fishing string S, enters the ports 28 in the upper end of the wash pipe, is discharged into the fish bore and returns to the surface through the radial ports in the sub and the annulus surrounding the fishing string S.

This prior practice requires the pulling and re-running of the fishing string S, the replacement of the sub 14 and the re-establishing of the connection to the fish F, all of which requires excessive time and presents difliculties. The establishing of circulation in the method of the present invention between the bore of the fishing string and the annulus surrounding the fishing string is achieved without any manipulation of the fishing string S and while maintaining the connection between the retrieving assembly R and the fish F. Such circulation is readily and simply established with the sub 14 of the present invention by increasing the pressure in the fishing string to a preselected pressure to open the normally closed radial port provided in the sub 14 as hereinafter more fully'explained, Thus, circulation may be selectively established for operation of the wash pipe 18 or for any other operation, such as circulation of mud into the annulus to control the well or to unload the liquid column in the fishing string S as it is pulled.

Using the improved sub 14 of the present invention, the communication between the interior and the exterior of the fishing string S is normally closed but may be selectively established by increasing the pressure of the fluid in the fishing string S. To have such a communication which may be selectively established, the sub '14 is provided with a passage 30 extending through the body 32 from the bore 34 to the exterior of the body 32. Passage 30 is normally closed by the pressure responsive means 36. As shown in FIGURE 1, the pressure responsive means 36 includes the rupturable diaphragm 38 38 which is held in sealing engagement against an outward facing shoulder in passage 30 by suitable means, such as the snap ring 40.

The sub 42 shown in FIGURE 2 is similar to the sub 14 and includes the passage 44 extending through the body 46 from the bore 48 to the exterior of the body 46 and the pressure responsive means 50 normally closing the passage 44. The pressure responsive means 50 includes a rupturable dia hragm 52 positioned against the outwardly facing shoulder 54 surrounding the passage 44 and the washer 56 which is held against the outer annular surface of diaphragm 52 by the annular nut 58. The nut 58 is tightened on the washer 56 with suflicient force to hold the diaphragm 52 in sealing relationship against the shoulder 54 at all times during normal operation.

Thus, with the sub 14 or the sub 42 connected in the retrieving assembly R, the pressure responsive means provides the structure normally closing the passage from the interior to the exterior of the fishing string S. The pressure responsive means may be selectively actuated to provide fluid communication from the interior of the fishing string to the annulus without the necessity of disconnecting the retrieveing assembly from the fish, pulling the string, replacing the sub, rerunning the string and re-establishing the safety joint connection.

Preselection of the pressure necessary to establish circulation is accomplished by selection of the rupturable diaphragm, with consideration being given to the fact that such diaphragms rupture responsive to the pressure differential on opposite sides thereof. Diaphragm rupture pressure is readily predicted from the strength of the diaphragm material, the thickness of the diaphragm and the effective unsupported area of the diaphragm exposed to pressure. The inner diameter of the washer 56 predetermines the unsupported or effective pressure area. The type of material selected and the thickness of the diaphragm predetermine the strength of the diaphragm. Therefore, it can readily be seen that by either varying the type of material, the thickness of material or the size of the opening through the washer 56 or snap ring 40, the desired pressure differential at which circulation is to be established from the interior of the pumpout sub to the exterior thereof may be readily and accurately predetermined. At any pressure differential less than the predetermined rupture pressure of the diaphragm, no circulation occurs through the sub. Once such predetermined rupture pressure differential has been reached by increasing the fluid pressure exerted on the inner side of the diaphragm, the diaphragm ruptures responsive to such pressure differential. Thereafter, regardless of the pressure of the circulating fluid, the communication has been established and remains established until the device has been removed from' the well and a new rupturable diaphragm installed in the sub.

It is within the scope of this invention to include a unit assembly to be installed in the passageway through the sub which includes a diaphragm, means determining the effective pressure area of the diaphragm and means for securing the unit within the body of the sub. Such units may be preassembled within an annular nut so that the units are readily replaceable. Such replaceable units also allow preselection of the pressure at which circulation is to be established through the sub immediately before running the fishing string by inserting the unit assembly in the sub having the preselected rupture pressure. It should be noted that since the rupture pressure of a frangible diaphragm is the pressure differential exerted across the effective area of the diaphragm the presence of a column of liquid in the well bore surrounding the fishing string exerts a pressure on the exterior of the diaphragm and must be taken into consideration in selecting the rupturable diaphragm to assure that the fluid pressure within the fishing string is suifieient to rupture the frangible diaphragm.

From the foregoing it can be seen that the present invention provides a new and improved method and apparatus for retrieving a fish from a well bore. The method includes the normal fishing operations of lowering a fishing string into a well bore, connecting to the fish, exerting an upward pull, jarring the fish and lowering a wash pipe through the interior of the fishing string so that the lower end of the wash pipe directs circulated fluids into the central bore of the fish and thereafter establishes circulation through the wash pipe and back upwardly through a portion of the fishing string S and out through the selectively established communication in the sub once the preselected pressure has been reached by the circulating fluid to cause the pressure responsive means to establish circulation without having to disconnect from the fish and pull the retrieving assembly to establish such circulation. Also provided is an improved sub configuration, through which communication is normally closed until a preselected pressure differential is reached on the interior of the sub with respect to exterior pressure.

Although the preferred form of providing a normally closed port which may be selectively opened includes the diaphragm, it is evident that other pressure responsive means may be employed. For example, the port may be normally closed by a spring-pressed valve element which would remain closed until a predetermined pressure, sufiicient to overcome the spring, is built up within the fishing string. The important feature is to provide a sub having a normally closed port, which port may be selectively opened under predetermined pressure conditions.

The selective opening of the port has been described in connection with the fishing or retrieving operation and in the event that a washing out of the bore of the fish is necessary. However, it is pointed out that the provision of a port which may be selectively opened has other advantages. For example, if during the fishing operation excessive pressure builds up in the lower end of the well bore to the point where a blowout condition might be present, heavy drilling mud may be pumped downwardly through the annulus and its pressure utilized to rupture the diaphragm, whereby the drilling mud may be pumped downwardly through the fish to the lower end of the well "bore and thereby control the blowout condition. Also in some instances, it may be desirable after the fish has been pulled, to build up the pressure and fracture the disc. Thereafter, if the spring is pulled from the well bore, I

the fluid within the string would escape through the radial port or ports, and this would obviate having to pull a wet string.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as Well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

1. The method of retrieving a fish stuck in a well bore, including the steps of lowering a fishing string having an internal seat into the well bore,

engaging the fish with the lower end of the fishing string,

manipulating the fishing string to exert forces on the lowering a wash pipe downwardly through the fishing string to a position at which the lower end of the wash pipe is directed into the bore of the fish and the upper end seats on said internal seat in said fishing string,

establishing communication for circulation of fluid through a normally closed passage from the interior to the exterior of said fishing string at a point below said internal seat while said fishing string remains in engagement with said fish,

circulating fluid through said fishing string and said wash pipe into the bore of said fish to Wash material therefrom,

said fluid and material flowing through said passage and up the annulus to the surface of the well bore, and

manipulating the fishing string after circulation is established to exert forces on said fish.

2. The method according to claim 1 wherein,

once said communication is established through said normally closed passage it is maintained established independent of fluid pressure while said fishing string remains in said well bore.

3. The method of retrieving a fish stuck in a well bore with a fishing string having a retrieving assembly which includes a rupturable diaphragm closing a radial passage in the wall of the retrieving assembly, including the steps of lowering the retrieving assembly on said fishing string into the well bore,

connecting the lower end of the retrieving assembly with the fish,

manipulating the fishing string to exert forces on said lowering a wash pipe into said fishing string,

increasing the pressure of fluid in said fishing string to a pressure sufficient to rupture said diaphragm and thereby establish fluid communication .between the interior and exterior of said retrieving assembly while said retrieving assembly remains connected to said fish, and

circulating fluid down through said fishing string and said wash pipe after said diaphragm is ruptured to wash material from the bore of said fish.

4. In a retrieving assembly which is used to retrieve a fish stuck in a well bore, the improvement comprising a first sub having a tubular body and defining an upwardly facing seaL surrounding the central bore through said body,

a wash pipe seatable on said seat,

a second sub having a tubular body with a central bore therethrough,

said second sub connected below said first sub in said retrieving assembly,

said body of said second sub defining a pasageway communicating from the exterior of said body to the central bore of said body, and pressure-responsive means mounted in said body of said second sub to normally close said passage and being adapted to establish communication through said passage responsive to a preselected fluid pressure within the central bore of said second sub body. 5. An assembly according to claim 4, wherein said pressure-responsive means comprises a frangible disc, means securing said frangible disc in said body closing said passage, said frangible disc adapted to rupture responsive to a preselected fluid pressure within said central bore of said body to establish communication through said pasage. 6. An assembly according to claim 5, wherein said securing means comprises an outwardly facing shoulder surrounding said passage against which said frangible disc is positioned, and a snap ring engaging said body surrounding said passage and said frangible disc to retain said frangible disc against said shoulder. 7. An assembly according to claim 5, wherein said securing means comprises an outwardly facing shoulder surrounding said passage against which said frangible disc is positioned, an annular washer positioned against the outer side of said frangible disc and defining a preselected central area through which said frangible disc ruptures when exposed to a preselected fluid pressure, and means holding said frangible disc and said washer in position in said passage. 8. An assembly according to claim 4, wherein said 7 pressure-responsive means comprises a frangible disc having a preselected thickness positioned in said body across said passage,

an annular washer having a preselected inner diameter positioned in said body against the side of said disc which faces the exterior of said body, and means securing said disc and said washer in said body across said passage.

9. A retrieving assembly for retrieving a stuck fish from within a well bore, comprising a fishing string adapted to be lowered within a well bore and having a central bore therethrough,

means connected on the lower end of said fishing string for engaging a fish,

a first sub connected in said fishing string and having a tubular body defining an upwardly facing seat surrounding the central bore through said body,

a wash pipe seatable on said seat,

a second sub connected in said fishing string below said first sub and having a tubular body with a central bore therethrough,

said body of said second sub defining a passage communicating from the exterior of said body to the central bore of said body, and

pressure-responsive means mounted in said body of said second sub to normally close said passage and being adapted to establish communication through said passage responsive to a preselected fluid pressure within the central bore of said second sub body.

10. A retrieving assembly according to claim 9 wherein said pressure-responsive means comprises,

a frangible disc having a preselected thickness positioned in said body across said passage to normally close said passage,

an annular washer having a preselected inner diameter positioned in said body against the side of said disc which faces the exterior of said body, and

means securing said disc and said washer in said body across said passage.

11. A retrieving assembly for retrieving a stuck fish from within a well bore, comprising a fishing string adapted to be lowered within the well bore,

means on said fishing string for engaging a fish stuck in a well bore,

an upwardly facing seat defined on the interior of said fishing string near the lower end thereof,

a pump-out sub connected in said fishing string below said seat and above said engaging means and defining a radial port extending through its wall,

means exposed to the pressure within the fishing string normally closing said radial port and constructed LO open said port upon a predetermined pressure being applied to the interior of said sub, and

a wash pipe adapted to be lowered into said fishing string,

said wash pipe defining a shoulder adapted to seat on and seal against said upwardly facing seat and a projection therebelow whereby when said wash pipe is seated on said seat and pressure in said fishing string is increased above said predetermined pressure, said port is open to establish circulation downwardly through said wash pipe and to the exterior of said fishing string through said port.

References Cited UNITED STATES PATENTS JAMES A. LEPPINK, Primary Examiner.

US. Cl. X.R. 

